text: Sort the biotonic doubly linked list | C ++ implementation to sort the biotonic doubly linked list ; a node of the doubly linked list ; Function to reverse a Doubly Linked List ; swap next and prev for all nodes of doubly linked list ; Before changing head , check for the cases like empty list and list with only one node ; Function to merge two sorted doubly linked lists ; If first linked list is empty ; If second linked list is empty ; Pick the smaller value ; function to sort a biotonic doubly linked list ; if list is empty or if it contains a single node only ; if true , then ' current ' is the first node which is smaller than its previous node ; move to the next node ; if true , then list is already sorted ; spilt into two lists , one starting with ' head ' and other starting with ' current ' ; reverse the list starting with ' current ' ; merge the two lists and return the final merged doubly linked list ; Function to insert a node at the beginning of the Doubly Linked List ; allocate node ; put in the data ; since we are adding at the beginning , prev is always NULL ; link the old list off the new node ; change prev of head node to new node ; move the head to point to the new node ; Function to print nodes in a given doubly linked list ; if list is empty ; Driver program to test above ; Create the doubly linked list : 2 < -> 5 < -> 7 < -> 12 < -> 10 < -> 6 < -> 4 < -> 1 ; sort the biotonic DLL
code: #include <bits/stdc++.h> NEW_LINE using namespace std ; struct Node { int data ; struct Node * next ; struct Node * prev ; } ; void reverse ( struct Node * * head_ref ) { struct Node * temp = NULL ; struct Node * current = * head_ref ; while ( current != NULL ) { temp = current -> prev ; current -> prev = current -> next ; current -> next = temp ; current = current -> prev ; } if ( temp != NULL ) * head_ref = temp -> prev ; } struct Node * merge ( struct Node * first , struct Node * second ) { if ( ! first ) return second ; if ( ! second ) return first ; if ( first -> data < second -> data ) { first -> next = merge ( first -> next , second ) ; first -> next -> prev = first ; first -> prev = NULL ; return first ; } else { second -> next = merge ( first , second -> next ) ; second -> next -> prev = second ; second -> prev = NULL ; return second ; } } struct Node * sort ( struct Node * head ) { if ( head == NULL head -> next == NULL ) return head ; struct Node * current = head -> next ; while ( current != NULL ) { if ( current -> data < current -> prev -> data ) break ; current = current -> next ; } if ( current == NULL ) return head ; current -> prev -> next = NULL ; current -> prev = NULL ; reverse ( & current ) ; return merge ( head , current ) ; } void push ( struct Node * * head_ref , int new_data ) { struct Node * new_node = ( struct Node * ) malloc ( sizeof ( struct Node ) ) ; new_node -> data = new_data ; new_node -> prev = NULL ; new_node -> next = ( * head_ref ) ; if ( ( * head_ref ) != NULL ) ( * head_ref ) -> prev = new_node ; ( * head_ref ) = new_node ; } void printList ( struct Node * head ) { if ( head == NULL ) cout << " Doubly ▁ Linked ▁ list ▁ empty " ; while ( head != NULL ) { cout << head -> data << " ▁ " ; head = head -> next ; } } int main ( ) { struct Node * head = NULL ; push ( & head , 1 ) ; push ( & head , 4 ) ; push ( & head , 6 ) ; push ( & head , 10 ) ; push ( & head , 12 ) ; push ( & head , 7 ) ; push ( & head , 5 ) ; push ( & head , 2 ) ; cout << " Original ▁ Doubly ▁ linked ▁ list : n " ; printList ( head ) ; head = sort ( head ) ; cout << " Doubly linked list after sorting : n " ; printList ( head ) ; return 0 ; }